The ongoing revolution in the preparation of nano-engineered materials continues to spawn new combinations of elements and compounds. Many of these new materials may include exotic phase mixtures (composites) or layered thin film structures (devices), resulting in new and unusual properties that may result directly from the spatial relationships and nano-structural arrangements of the material components. Increasingly, these new materials must be characterized at the molecular or atomic level using microscopy techniques such as Scanning Probe Microscopy (SPM), Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM), among others.
Sample preparation for multi-phase materials traditionally involves embedding the sample in a support matrix followed by abrasive polishing or microtome slicing to achieve a smooth surface or thin section. In the case of layered thin film devices, the samples were generally cleaved (broken) or otherwise cut into smaller pieces, sandwiched between support materials, and then polished smooth. These techniques were well-suited for materials that could withstand abrasive reduction and where charging effects could be circumvented by the addition of a conductive path.
The use of focused ion beam (FIB) systems has became a valuable, albeit time consuming, tool for sampling precise site-specific sub-surface features in multi-phase materials or thin film devices. Though FIBs have become faster at removing a wide range of materials, the excavated area is typically very small (2,000 μm3). In addition, many novel materials may contain organic fibers and polymers, rendering them less suitable for FIB milling due to an associated charge build-up or adverse sputtering properties.
Increasingly, new combinations of exotic materials used in multi-phase and multi-layered thin films are poorly-suited to either mechanical polishing or FIB milling. Softer materials tend to smear or become delaminated from neighboring structures, while hard or brittle materials may fracture or shed particles into neighboring regions, either result constituting an unacceptable alteration of the original structure of the sample material. Similarly, composite materials may exhibit distortion of discrete grains or phases as a result of the shearing forces of polishing, altering critical spatial information and introducing chemical anomalies that affect subsequent EDX or surface analysis results.
Examples of sample preparation and microscopic analyses may be found in the following references: Alani et al., Instrumentation for SEM Specimen Preparation of Semiconductors, Recent Advances in Broad Ion Beam Techniques, Feb. 1, 2000; Smith et al., Applied Surface Science 255 (2008) 1606-1609; Langford et al., J. Vac. Sci. Technol. A19, 982 (2001); Hauffe et al., 3D Microscopy and Microanalysis of Heterogeneous SEM Samples by Broad Ion Beam Processing: Cutting-Etching-Coating, 1997; Hauffe, Broad Ion Beam (BIB) Slope Cutting through Sn-Coated Copper Wires for 3D Scann9ing Electron Microscopy and Microanalysis, Microsc Microanal 13 (Suppl 2) 2007; Ogura et al., New Methods for Cross-Section Sample Preparation Using Broad Argon Ion Beam, Microsc Microanal 13 (Suppl 2), 2007; Haight et al., J. Vac. Sci. Technol. B 17, 3137 (1999); MacLean et al., Nano Lett., 2010, 10(3), pp 1037-1040; Petzold et al., Micro Structure Analysis for System in Package Components—Novel Tools for Fault Isolation, Target Preparation, and High-resolution Material Diagnostics, Electronic Components and Technology Conference ECTC, Las Vegas, Session 29, Apr. 6, 2010, each of which is hereby incorporated by reference.
Selected examples of sample preparation and microscopic analyses may be found in the following patent documents: Todoroki et al., U.S. Patent Appl. Publ., U.S. 2008/0067443 A1; Coyle et al., U.S. Patent Appl. Publ. 2012/0085923; Coyle et al., U.S. Patent Appl. Publ., 2012/0085937; Coyle et al., U.S. Patent Appl. Publ., 2012/0085938; Coyle et al., U.S. Patent Appl. Publ., 2012/0085939; Smith, U.S. Pat. No. 3,622,782; Franks, U.S. Pat. No. 4,128,765; Masuzawa et al., U.S. Patent No. 4,574,179; Tokiguchi et al., U.S. Pat. No. 4,658,143; Swann et al., U.S. Pat. No. 5,472,566; Yoshioka et al., U.S. Pat. No. 5,907,157; Grünewald, U.S. Pat. No. 5,986,264; Birk et al., U.S. Pat. No. 6,710,918; Alani, U.S. Pat. No. 6,768,110; Shichi et al., U.S. Pat. No. 7,700,931; Cuomo et al., U.S. Pat. No. 4,381,453; Haight et al., U.S. Pat. No. 6,333,485; Hasegawa, et al., U.S. Pat. No. 7,722,818; Sugizaki, U.S. Pat. No. 7,952,082; Kagaya, U.S. Pat. No. 8,008,635; Coyle, et al., U.S. Pat. No. 8,283,642, the disclosures of each of which are hereby incorporated by reference for any and all purposes.